This also requires the 64-bits rust compiler and some build system
tweaks.
And since we make the 32-bits builds cross-compiles on CI, we also need
to adjust the MSVC build mozconfigs such that the host compiler points
to the right MSVC cl. Likewise, the DIA SDK is used for host things, so
use the 64-bits version or it.
Differential Revision: https://phabricator.services.mozilla.com/D7845
--HG--
extra : moz-landing-system : lando
